2001 Lexus GS 430 Knock Sensor

We should start with what the actual code was. Can you provide the code and then we can be sure to point you in the right direction?

As for the knock sensor, here is a guide that will help with explaining what it is and what can happen:

https://www.2carpros.com/articles/how-a-knock-sensor-works

Lower octane fuel can cause pinging and that is what the knock sensor is supposed to sense and adjust the fuel to address the ping/detonation.

Please check the codes again and let us know what the code is so that we can be sure we are doing the correct testing.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Let me know what questions you have. Thanks